(compile-reinitialize-errors): Rename first arg from ARGP to REPARSE.

(compile-reinitialize-errors): Rename first arg from ARGP to REPARSE.
Test only its nilness.
(compile-goto-error): Pass (consp ARGP) to compile-reinitialize-errors
instead of ARGP itself.
(next-error): Code broken out into two new functions; call them.
(compilation-next-error-locus): New function; bulk of code from next-error.
Silently skip errors whose source loci are markers in killed buffers.
(compilation-goto-locus): New function, final code from next-error.